/*
 * Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the Classpath exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package org.openjdk.btrace.agent;

import org.openjdk.btrace.core.DebugSupport;
import org.openjdk.btrace.core.SharedSettings;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * This class represents various strategies available for dumping BTrace
 * output to a file.
 *
 * @author Jaroslav Bachorik
 */
abstract class TraceOutputWriter extends Writer {
    protected final DebugSupport debug;

    protected TraceOutputWriter(SharedSettings settings) {
        debug = new DebugSupport(settings);
    }

    /**
     * Plain file writer - all output will go to one specified file
     *
     * @param output   The file to put the output to
     * @param settings The settings storage
     * @return Returns an appropriate {@linkplain  TraceOutputWriter} instance or NULL
     */
    public static TraceOutputWriter fileWriter(File output, SharedSettings settings) {
        TraceOutputWriter instance = null;
        try {
            instance = new SimpleFileOutput(output, settings);
        } catch (IOException e) {
            // ignore
        }
        return instance;
    }

    /**
     * Time based rolling file writer. Defaults to 100 allowed output chunks.
     *
     * @param output   The file to put the output to
     * @param settings The shared settings
     * @return Returns an appropriate {@linkplain  TraceOutputWriter} instance or NULL
     */
    public static TraceOutputWriter rollingFileWriter(File output, SharedSettings settings) {
        TraceOutputWriter instance = null;
        try {
            instance = new TimeBasedRollingFileWriter(output, settings);
        } catch (IOException e) {
            // ignore
        }
        return instance;
    }

    private static void ensurePathExists(File f) {
        if (f == null || f.exists()) return;

        ensurePathExists(f.getParentFile());

        if (!f.getName().endsWith(".btrace")) { // not creating the actual file
            try {
                f.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
                // ignore and continue
            }
        }
    }

    private static class SimpleFileOutput extends TraceOutputWriter {
        private final FileWriter delegate;

        @SuppressWarnings("DefaultCharset")
        public SimpleFileOutput(File output, SharedSettings settings) throws IOException {
            super(settings);
            try {
                File parent = output.getParentFile();
                if (parent != null) {
                    output.getParentFile().mkdirs();
                }
                delegate = new FileWriter(output);
            } catch (IOException e) {
                debug.debug(e);
                throw e;
            }
        }

        @Override
        public void close() throws IOException {
            delegate.close();
        }

        @Override
        public void flush() throws IOException {
            delegate.flush();
        }

        @Override
        public void write(char[] cbuf, int off, int len) throws IOException {
            delegate.write(cbuf, off, len);
        }
    }

    @SuppressWarnings("DefaultCharset")
    private abstract static class RollingFileWriter extends TraceOutputWriter {
        protected final SharedSettings settings;
        private final ReentrantReadWriteLock writerLock = new ReentrantReadWriteLock();
        private final String path, baseName;
        // @GuardedBy writerLock
        private FileWriter currentFileWriter;
        private int counter = 1;

        public RollingFileWriter(File output, SharedSettings settings) throws IOException {
            super(settings);
            try {
                output.getParentFile().mkdirs();
                currentFileWriter = new FileWriter(output);
                path = output.getParentFile().getAbsolutePath();
                baseName = output.getName();
                this.settings = settings;
            } catch (IOException e) {
                debug.debug(e);
                throw e;
            }
        }

        @Override
        public final void close() throws IOException {
            try {
                writerLock.readLock().lock();
                currentFileWriter.close();
            } finally {
                writerLock.readLock().unlock();
            }
        }

        @Override
        public final void flush() throws IOException {
            try {
                writerLock.readLock().lock();
                currentFileWriter.flush();
            } finally {
                writerLock.readLock().unlock();
            }

            if (needsRoll()) {
                nextWriter();
            }
        }

        @Override
        public final void write(char[] cbuf, int off, int len) throws IOException {
            try {
                writerLock.readLock().lock();
                currentFileWriter.write(cbuf, off, len);
            } finally {
                writerLock.readLock().unlock();
            }
        }

        private void nextWriter() {
            try {
                writerLock.writeLock().lock();
                currentFileWriter = getNextWriter();
            } catch (IOException e) {
                debug.debug(e);
            } finally {
                writerLock.writeLock().unlock();
            }
        }

        private FileWriter getNextWriter() throws IOException {
            currentFileWriter.close();
            File scriptOutputFile_renameFrom = new File(path + File.separator + baseName);
            File scriptOutputFile_renameTo = new File(path + File.separator + baseName + "." + (counter++));

            if (scriptOutputFile_renameTo.exists()) {
                scriptOutputFile_renameTo.delete();
            }
            scriptOutputFile_renameFrom.renameTo(scriptOutputFile_renameTo);
            scriptOutputFile_renameFrom = new File(path + File.separator + baseName);
            if (counter > settings.getFileRollMaxRolls()) {
                counter = 1;
            }
            return new FileWriter(scriptOutputFile_renameFrom);
        }

        protected abstract boolean needsRoll();
    }

    private static class TimeBasedRollingFileWriter extends RollingFileWriter {
        private final TimeUnit unit = TimeUnit.MILLISECONDS;
        private long lastTimeStamp = System.currentTimeMillis();

        public TimeBasedRollingFileWriter(File output, SharedSettings settings) throws IOException {
            super(output, settings);
        }

        @Override
        protected boolean needsRoll() {
            long currTime = System.currentTimeMillis();
            long myInterval = currTime - lastTimeStamp;
            if (unit.convert(myInterval, TimeUnit.MILLISECONDS) >= settings.getFileRollMilliseconds()) {
                lastTimeStamp = currTime;
                return true;
            }
            return false;
        }
    }
}
